KBySV028shoooo

Hunt Hypothesis

This hunt hypothesis targets adversaries leveraging specific file-based indicators defined by the KBySV028shoooo YARA signature to identify early-stage malware or suspicious artifacts within the environment. Proactive hunting for this rule in Azure Sentinel is essential to detect low-severity anomalies that may represent initial footholds, allowing the SOC team to investigate potential threats before they escalate into significant incidents.

YARA Rule

rule KBySV028shoooo
{
      meta:
		author="malware-lu"
strings:
		$a0 = { 68 [4] E8 01 00 00 00 C3 C3 60 8B 74 24 24 8B 7C 24 28 FC B2 80 33 DB A4 }

condition:
		$a0 at pe.entry_point
}

Deployment Notes

This YARA rule can be deployed in the following contexts:

• Microsoft Defender for Endpoint — Custom indicators / advanced hunting
• Email Gateway — Attachment scanning
• File Share Monitoring — Periodic scanning of shared drives
• YARA CLI — Manual threat hunting on endpoints

This rule contains 1 string patterns in its detection logic.

• Source Rule

False Positive Guidance

Here are 4 specific false positive scenarios for the detection rule KBySV028shoooo, including suggested filters and exclusions tailored for a legitimate enterprise environment:

• Scenario: Automated Software Deployment via SCCM

  • Context: The System Center Configuration Manager (SCCM) client service (ccmexec.exe) frequently executes deployment scripts or extracts application payloads in the C:\Windows\CCMCache directory. These actions often involve creating temporary executable files that match the YARA signature pattern of KBySV028shoooo, triggering alerts for every software update cycle.
  • Suggested Filter/Exclusion: Create an exclusion based on the process path and parent process name.
    • Filter: ProcessPath contains "C:\Program Files (x86)\Microsoft Configuration Manager\ccmexec.exe" AND ParentProcessName = "ccmexec.exe"

• Scenario: Scheduled Antivirus Definition Updates

  • Context: The Microsoft Defender Antivirus service (MsMpEng.exe) runs scheduled jobs to download and install new virus definition updates. During this process, it extracts compressed signature files which may contain the specific byte sequences or strings defined in the KBySV028shoooo rule, causing recurring alerts during maintenance windows (e.g., 3:00 AM daily).
  • Suggested Filter/Exclusion: Exclude events originating from the Microsoft Defender service process.
    • Filter: ProcessName = "MsMpEng.exe" AND ProcessPath starts with "C:\Program Files\Windows Defender\"

• Scenario: Endpoint Backup Agent Execution

  • Context: The Veeam Endpoint Backup agent (veeamagent.exe) performs incremental backups by scanning and compressing user data. When the agent processes specific file types (such as .dll or .exe within user profiles), it